What is this all about?
This tutorial will turn your Raspberry PI into a simple Bluetooth audio receiver, which plays music through connected speakers. It's like a regular car audio system, but it can be used anywhere and it's a good value.
Audio source (i.e. smartphone) | v ((( Wireless Bluetooth Channel ))) | v Raspberry PI | v USB Audio Interface | v Speakers
The Bluetooth profile which does the magic is called A2DP.
pi@raspberrypi:~ $ lsusb ... Bus 001 Device 008: ID 041e:30d3 Creative Technology, Ltd Sound Blaster Play! ... Bus 001 Device 012: ID 0a12:0001 Cambridge Silicon Radio, Ltd Bluetooth Dongle (HCI mode) ...
The on–board audio produces low–quality, noisy output, so I decided to use something better. I chose external USB Creative Sound Blaster Play! interface. It costs ~$20.
As for Bluetooth dongle, I used Digitus Tiny USB-Adapter, which is discovered as
Cambridge Silicon Radio, Ltd Bluetooth Dongle.
Note: I used another dongle (different manufacturer) also discovered as
Cambridge Silicon Radio but unable to stream audio. So beware, because different manufacturers use the same hardware in a different way. Or they pretend to use the same hardware for some (compatibility?) reasons. This way or another, if you get garbled audio or no audio at all but everything else is alright, don't worry, just try another dongle – it's cheap.
See RPi USB Bluetooth adapters for buying recommendations. Trial and error is another option, since most devices cost below $10.
Raspberry PI offers limited power to USB devices (and limited number of ports). You'll need some active (powered) USB Hub to keep USB devices stable and working (USB Audio, USB Bluettoth and optional USB WiFi). Google to learn more, it's a very common topic when using Raspberry PI.
sudo apt-get update sudo apt-get upgrade
Note: It usually takes a while. Get some tee and sandwiches.
Then install required packages (related article):
sudo apt-get install alsa-utils bluez bluez-tools pulseaudio-module-bluetooth python-gobject python-gobject-2
Not quite sure it's really needed (?), but it doesn't hurt:
sudo usermod -a -G lp pi
Use the following configuration to get most of PulseAudio (related article):
pi@raspberrypi:~ $ cat /etc/pulse/daemon.conf ... resample-method=ffmpeg enable-remixing = no enable-lfe-remixing = no default-sample-format = s32le default-sample-rate = 192000 alternate-sample-rate = 176000 default-sample-channels = 2 exit-idle-time = -1 ...
Note: PA is pretty CPU–consuming. With the following configuration it uses ~30% of my PI's CPU.
So if you expect PI to do something else beside A2DP and avoid sound glitches, reasearch different
Configure USB Audio
The problem is that on–board audio ouput is prefered over USB audio interface:
pi@raspberrypi:~ $ cat /proc/asound/modules 0 snd_bcm2835 1 snd_usb_audio
Some configuration does the trick (related article):
pi@raspberrypi:~ $ cat /etc/modprobe.d/alsa-base.conf # This sets the index value of the cards but doesn't reorder. options snd_usb_audio index=0 options snd_bcm2835 index=1 # Does the reordering. options snd slots=snd-usb-audio,snd-bcm2835
From now on RPI uses USB Audio as default:
pi@raspberrypi:~ $ cat /proc/asound/modules 0 snd_usb_audio 1 snd_bcm2835
Make sure Bluetooth audio is working and discovered as a car audio system
pi@raspberrypi:~ $ cat /etc/bluetooth/audio.conf [General] Class = 0x20041C Enable = Source,Sink,Media,Socket
I'm not quite sure if the following is also needed. But I added it anyway:
pi@raspberrypi:~ $ cat /etc/bluetooth/main.conf [General] ... Name = raspberrypi Class = 0x20041C ...
Pair devices (phones, tablets, PCs) with PI using
pi@raspberrypi:~ $ bluetoothctl
See that your USB dongle is here:
[bluetooth]# list Controller 00:1A:7D:DA:71:06 raspberrypi [default]
Prepare for pairing:
[bluetooth]# agent on [bluetooth]# default-agent [bluetooth]# discoverable on [bluetooth]# scan on
Then, for each device:
pair XX:XX:XX:XX:XX:XX ... Go through pairing process. ... trust XX:XX:XX:XX:XX:XX
CTRL(CMD)+D to exit
Setup auto connecting
Given that your device is already paired and connected to PI, run the following:
pi@raspberrypi:~ $ pactl list sources short 0 alsa_output.0.analog-stereo.monitor module-alsa-card.c s16le 2ch 48000Hz IDLE 1 alsa_input.0.analog-mono module-alsa-card.c s16le 1ch 48000Hz IDLE 4 bluez_source.A8_88_08_11_AB_4B module-bluez5-device.c s16le 2ch 44100Hz RUNNING
pi@raspberrypi:~ $ pactl list sinks short 0 alsa_output.0.analog-stereo module-alsa-card.c s16le 2ch 48000Hz RUNNING
The whole trick is to redirect the right source (i.e. smartphone) the right sink (ALSA) each time a new Bluetooth device is connected. In the above case, it would be
The good news that it can be automated. Add udev rule which executes
a2dp-autoconnect script each time a Bluetooth device is connected:
pi@raspberrypi:~ $ cat /etc/udev/rules.d/99-input.rules KERNEL=="input[0-9]*", RUN+="/home/pi/a2dp-autoconnect"
The script I used is an extended version of http://blog.mrverrall.co.uk/2013/01/raspberry-pi-a2dp-bluetooth-audio.html. It's pretty straightforward: it redirects a new Bluetooth audio source to the right sink and sets output volume level.
I located it in
/home/pi/a2dp-autoconnect, then made it executable:
pi@raspberrypi:~ $ chmod +x a2dp-autoconnect
Note: Observe connection log "live" to debug connection issues:
pi@raspberrypi:~ $ tail -f /var/log/a2dp-autoconnect
Some people complained that the whole configuration does not work after reboot, unless
pi user is logged in.
Auto–login can be enabled using
pi@raspberrypi:~ $ sudo raspi-config
in "Boot Options" -> "Console Auto–login".
If your device is already paired, simply connect it to Raspberry PI and select Bluetooth audio output. Enjoy your tunes!
Tested with iPhone, MacbookPro and Windows laptop.